Autogenous bone grafting is the most common procedure used to treat continuity defects of bone, frequently encountered after rumor surgery, trauma, or in the case of congenital deformities. Unfortunately, a variable portion of the grafted bone is resorbed by the surrounding soft tissues, being replaced by fibrous scar tissue. This may result in inadequate final bone strength or volume, thus necessitating re-operation and re-grafting. The purpose of this study is to evaluate the hypothesis that isolation of the bone graft from adjacent soft tissues using a biocompatible membrane will decrease the amount of resorption and result in a significantly greater volume and density of final bone bridging the defect. Eighteen rabbits will have one of 6 surgical procedures performed on both left and right tibia. The 36 tibia will be divided into 6 surgical groups of 6 tibia each. One experimental group will have an 8mm continuity defect created and bridged by rigid bone plates. A second group will have the plated defect filled with an autogenous bone graft. A third group will have the bone graft isolated from the surrounding soft tissue with a biocompatible membrane, and a fourth group will have the membrane placed around the defect, without the bone graft. The final two groups will be controls, the first with no surgical procedure, and the second with the placement of bone plates without creation of a defect, to evaluate the possible stress shielding effects of the plates. Radiographs will be taken at times 0, 2, 4, and 6 months for quantitative evaluation. Fluorescent bone dyes will be injected at 2, 4, and 6 months to mark the areas actively mineralizing at these times. All animals will be sacrificed at 6 months, bones harvested, and analyzed with gross and microscopic measurements. Bone quantity, bone quality, and rates of bone formation will be compared, to determine if improved bone grafting results can be obtained with membrane barriers.